1. Technical Field
The present invention is directed toward bicycle brakes, and more particularly toward a structure for adjustably attaching a disc brake caliper to a bicycle frame.
2. Background Art
Disc brakes for bicycles are growing in popularity as consumers demand and bicycle manufacturers strive to provide ever advancing technology on bicycles. Disc brake systems generally consist of a rotor which is fixedly attached to the hub of a bicycle wheel and a caliper which is fixedly attached to a wheel supporting portion of the bicycle frame and which receives the rotor between a pair of bike pads which are advanced into and out of contact with the rotor along a select axis. The wheel supporting portion of the frame has some structure for attaching the caliper to the chain or seat stay in the rear or fork in the front of the frame. This structure typically consists of a boss or a pair of bosses which extend from the frame substantially parallel to the plane of the rotor and which have internally threaded bores in their distal ends which are intended to lie in a plane normal to the plane of the rotor. The caliper, in turn, has a mounting foot which extends from the caliper body and includes a pair of holes corresponding to the bores in the ends of the attachment bosses. The caliper is then bolted to the frame by bolts axially received the holes in the mounting foot. When properly aligned, the rotor will be received between the brake pads of the caliper so that the brake pads of the caliper are advanced into and out of contact with the rotor along an axis that is normal to the plane of the rotor.
Assuming that the attachment bosses extend parallel to the plane of the rotor and that the ends of the attachment bosses lie in a plane perpendicular to the plane of the rotor, prior art calipers would be properly aligned with the brake pads being advanced along an axis normal to the rotor. In practice, however, the normal range of manufacturing tolerances in the bicycle and caliper makes it unlikely that the caliper will be properly aligned with respect to the rotor. When the caliper is not properly aligned, the brake pads will not strike the rotor flush which can degrade brake performance. It can even lead to the brake pads rubbing against the rotor and deteriorating bicycle performance.
One structure known in the prior art for addressing this improper alignment is providing elongate slots on the mounting foot of the caliper corresponding to the bores in the mounting bosses which extend substantially parallel to the select axis of advancement of the pads. These slots allow translational movement of the caliper toward and away from the rotor to precisely position the rotor intermediate the pads of the caliper. In addition, these slots enable the caliper to be canted about an axis parallel to an axis of the mounting boss bores to compensate for some misalignment between the rotor and the caliper. However, because these slots only allow for translational movement and some range of canting, they do not enable proper alignment with the rotor if the tolerances cause misalignment outside of these limited directions of travel.
The present invention is directed toward overcoming one or more of the problems discussed above.
The present invention is an attachment structure for a caliper of a disc brake assembly consisting of a caliper and a rotor. The caliper is attached to a wheel supporting portion of a cycle frame which supports a wheel with the rotor fixedly attached to the wheel and the rotor lying in a fixed plane relative to the supporting portion of the frame. The supporting portion of the frame has a pair of attachment bores oriented to attach the caliper with the rotor received between a pair of brake pads advanced into and out of contact with the rotor by the caliper along a select axis. The attachment structure allows for infinite variation of the angle of incidence between the select axis and the plane of the rotor within a defined range. Attachment bolts secure the caliper to the frame with a select angle of incidence between the select axis and the plane of the rotor.
Another aspect of the present invention is a disc brake assembly attachable to a wheel supporting portion of a frame of a cycle. The disc brake assembly includes a rotor fixedly attached to a wheel mounted to the wheel supporting portion of the frame, with the rotor residing in a plane of fixed orientation relative to the wheel supporting portion of the frame. A caliper receives the rotor between a pair of brake pads with the caliper advancing the brake pads into and out of contact with the rotor along a select axis. An attachment structure attaches the caliper to the wheel supporting portion of the frame with the angle of incidence between the select axis and the plane of rotor being infinitely variable within a defined range. In this manner, the caliper can be aligned with the select axis normal to the rotor. At least one bolt is operatively associated with the attaching structure to secure the caliper to the frame with the select axis aligned normal to the rotor. The attaching structure preferably includes slots on the caliper substantially parallel to the select axis for enabling translational movement of the caliper toward and away from the rotor.
The attaching structure may include a pair of spaced bores on the wheel supporting portion of the frame defining a line substantially parallel to the plane of the rotor, the bores having openings which lie in a plane substantially normal to the plane of the rotor. A convex surface is associated with the mouth of each bore. A mating concave surface is associated with a bottom of a mounting foot of the caliper. Aligned holes extend through each of the concave and convex surfaces and correspond to the bores in the wheel supporting portion of the frame. A pair of slots in the mounting foot of the caliper also corresponds to the bores. These slots are substantially parallel to the select axis. A bolt having a head and a shaft is axially received in each slot, aligned hole and corresponding bore with the head protruding therefrom. The bolt is threadably engaged with the bores to maintain the caliper with the select axis aligned normal to the rotor. The attaching structure preferably further includes a pair of washers having mating concave and convex surfaces and opposite flat surfaces receiving the bolt with one of the flat surfaces abutting a top of the mounting foot of the caliper and the other of the flat surfaces abutting the head of the bolt.
In one embodiment, the mating concave and convex surfaces associated with the mouth of each bore and the underside of the mounting foot of the caliper comprise a pair of washers having mating concave and convex surfaces and opposite flat surfaces, with the washer pairs residing with one of the flat surfaces abutting the bottom of the caliper mounting foot and the other of the flat surfaces abutting the wheel supporting portion of the frame.
In another embodiment, the mating concave and convex surfaces associated with the mouth of each bore and the bottom of the mounting foot consists of a pair of plates having the mating concave and convex surfaces and opposite flat surfaces, the pair of plates further including the aligned holes, the plates residing with one flat surface abutting the bottom of the mounting foot and the other flat surface abutting the wheel supporting portion of the frame. Preferably, the aligned holes are elongate and correspond to the slots in the caliper mounting foot.
Yet another aspect of the present invention is a structure for attaching a caliper of a disc brake system to a cycle frame with a pair of brake pads advanced by the caliper in operative engagement with a rotor of the disc brake system, the frame having a pair of threaded caliper mounting bores and the caliper having a mounting foot. The attachment structure consists of mating concave and convex surfaces between the frame and a bottom of the caliper mounting foot to pivot the caliper about a pivoting axis. A pair of holes corresponding to the caliper mounting bores extend through the concave and convex mounting surfaces. A pair of spaced slots on the caliper mounting foot extend transverse the pivoting axis and are aligned with the holes and the mounting bores. A pair of bolts are axially received in the aligned slots, holes and the threaded mounting bores with the bolts engaging the threaded mounting bores to maintain the pads of the caliper in a select orientation relative to the rotor. The mating concave and convex surfaces may be a pair of washers residing between the bottom of the caliper mounting foot and the frame corresponding to each of the caliper mounting bores. Alternatively, the mating concave and convex surfaces residing between the bottom of the caliper mounting foot and the frame may be formed on a pair of elongate plates. Alternatively, one of the concave and convex surfaces may be on the bottom of the caliper mounting foot and the other may be on an elongate plate residing between the bottom of the caliper mounting foot and the frame. In this embodiment, the pair of holes in the elongate plate are preferably elongate to correspond to the slots in the caliper mounting foot. Preferably, mating concave and convex surfaces are further provided between the head of the bolt and the top of the caliper mounting foot. The mating concave and convex surfaces are preferably on a pair of washers corresponding to each of the bolt heads residing between the bolt heads and the top of the caliper mounting foot.
The structure for adjustably attaching a disc brake caliper to a bicycle frame of the present invention allows for infinite variation of the angle of incidence between an axis of movement of caliper brake pads and the plane of a rotor within a defined range. Thus, the caliper can be adjusted so that the select axis in is the desired orientation of normal to the plane of the rotor notwithstanding manufacturing tolerances and manufacturing defects that would cause the axis of pad travel of prior art calipers not to be normal to the plane of the rotor. In addition, the attachment structure allows translation of the caliper toward and away from the rotor to compensate for variations in the spacing between the attachment studs and the disc brake rotor amongst the bicycles of various manufacturers. The structure for adjustably attaching the disc brake is virtually self-adjusting within its defined range. The caliper can be readily self-aligned simply by loosening the attachment bolts, actuating the brake pads into abutment with the rotor and then tightening the attachment bolts. Thus, the many advantages of having the select axis of movement of the brake pads normal to the rotor can be achieved with minimal effort on the part of the user. Moreover, the structure providing these many advantages is inexpensive to manufacture and can be made from off the shelf parts making it an inexpensive solution to an otherwise vexing problem.